A typical protein skimmer comprises an upwardly open and downwardly closed tubular column having an inlet for contaminated water and an outlet for clean water. A bypass through an aerating pump has an intake that pulls in water from the column and an output that reinjects this water mixed with air bubbles back into the column. A scum collector is typically provided at the top of the column. Thus the organic solids in the dirty water stick to the bubbles and rise to the surface of the water where the bubbles dissipate, leaving the organics as scum that can be separated and disposed of. Such an apparatus is predominantly used in a salt-water aquarium.
Such a fractionater typically has a column of circular section and is oriented such that its open upper end is above the level of the water in the aquarium. The inlet for contaminated water from the aquarium is in the upper region of the column, the outlet for clean water back to the aquarium is in the lower end of the column, and the skimmer outlet is a bubbler in the lower region of the column above the outlet. Thus the water being purified flows slowly downward countercurrent to the rising bubbles. The aerating pump is preferably mounted outside the column and has a separate air inlet port open above the water level by means of which it draws in air for mixing with the water circulating through the pump. Another pump slowly moves the aquarium water into the column through the inlet and out via the outlet, typically returning the clean water to the bottom of the aquarium.
In the conventional design, the supply of contaminated is water into the upper region of the column housing is restricted. This is because if the water moved too briskly, turbulence would occur near the upper region of the in the skimmer so that the air bubbles or the foam forming as a result, would not be stable enough to remove the organics, but the air bubbles would burst and the organics would remain in the water. As a result, a controlled skimming operation could not be ensured. If the contaminants bound to the air bubbles were washed back into the aquarium of the system, undesired consequences would ensue, which means that special bacteria or algae would develop, which would be extremely stable and could be removed from the aquarium only with difficulty.
In addition it is disadvantageous that the contaminated water fed into the column from the aerating pump is already mixed with cleaned water, which limits the overall skimming performance of the skimmer. Furthermore, the pump can also aspirate more or less air from the skimming area itself, which means from the column, which may lead to a non-uniform and reduced amount of air in the air suction adapter, which would have a detrimental effect on the desired skimming operation.